Dissecting All Things Biological

From the tallest giraffe to the smallest bumble bee, there is an awe-inspiring spectrum of coat colour and pattern across the animal kingdom. However, it can be easy to think of a species, like the zebra for example, to be simply striped and each one look almost the same. What we fail to see without close inspection is the huge complexity and variability in these coat patterns.

This variation has been thought to play a major role in an animals’ chances of survival. It allows the avoidance of predators and parasites, regulation of body temperature and even allows individuals of the same species to recognise each other and therefore communicate. Despite it’s importance to the study of evolution little is known about the impacts of coat colouration on individual survival and species survival as a whole.

However, a recent study on Masai giraffes conducted by Dr Derek E. Lee and his team at the Wild Nature Institute, USA, has shed some light on this subject. The Masai giraffe is the tallest giraffe in the world, with adult males reaching up to 19.5 feet and females reaching 18 feet – or about 2.5 times the height of Michael Jordan. These giraffes are unique in that their coat pattern completely covers their limbs, unlike other species of giraffe which do not have patches on the legs.

Within each giraffe there is a high degree of variation in terms of colour and shape with patches ranging from those which are almost round with very smooth edges to those which are far less round with various indents.

In 1968 Anne Innis Dagg presented evidence that the shape, number, area and colour of spots on a giraffe’s coat could be passed on to offspring. These traits may have evolved because they possess the potential to camouflage offspring and therefore present a survival advantage.

Dr Lee and his team sampled wild Masai giraffes in northern Tanzania, East Africa to see if there was a correlation between coat pattern and survival rate of offspring. Their findings were consistent with the idea that both the size and shape of spots was relevant to the survival of the offspring, with the highest calf survival resulting from those with large spots that were either circular or irregular.

This is best explained by the theory of ‘enhanced background matching’ which suggests that the patterns on the offspring allow them to better match their surroundings. In the case of the giraffe, the dappled patterns on their coat match the patterns produced by light passing through the trees. This is where the offspring spend most of their time. The overall effect makes them less visible to predators and therefore less vulnerable to predation and increases chances of survival.

There is however some evidence that the spots could be linked to other survival-enhancing factors including visual communication with family members and other individuals or temperature regulation. Therefore it cannot be said with absolute certainty that camouflage thanks to their spot patterns is solely responsible for increased survival.

This unique research conducted by Dr Lee and his team is leading the way for other scientists to use the same tools used here to measure mammal coat patterns. This will only serve to enhance our understanding of the evolutionary advantages of coat pattern.